A power supply unit (PSU) start up sequence for a switched mode power supply (SMPS) may utilize a time controlled oscillator (TCO) during an initial start up period. As half-bridge (FIB) voltage feedback (VHBFB) becomes available, a controller for the PSU may hand over control of the operating system frequency from the TCO to a voltage controlled oscillator (VCO). Performance factors for the PSU start up period may include an amount of time needed for the PSU to provide a steady state output voltage, an amount of voltage overshoot and negative voltage slope during start up, as well as other factors. A PSU may be configured to supply a wide power range, which may impact the performance factors.